On-line early fault detection and diagnosis of municipal solid waste incinerators

A fault detection and diagnosis framework is proposed in this paper for early fault detection and diagnosis (FDD) of municipal solid waste incinerators (MSWIs) in order to improve the safety and continuity of production. In this framework, principal component analysis (PCA), one of the multivariate statistical technologies, is used for detecting abnormal events, while rule-based reasoning performs the fault diagnosis and consequence prediction, and also generates recommendations for fault mitigation once an abnormal event is detected. A software package, SWIFT, is developed based on the proposed framework, and has been applied in an actual industrial MSWI. The application shows that automated real-time abnormal situation management (ASM) of the MSWI can be achieved by using SWIFT, resulting in an industrially acceptable low rate of wrong diagnosis, which has resulted in improved process continuity and environmental performance of the MSWI.     

Hot waste-to-energy flue gas treatment using an integrated fluidised bed reactor

This paper describes an innovative process to increase superheated steam temperatures in waste-to-energy (WTE) plants. This solution is mainly characterised by a fluidised bed reactor in which hot flue gas is treated both chemically and mechanically. This approach, together with gas recirculation, increases the energy conversion efficiency, and raises the superheated steam temperature without decreasing the useful life of the superheater. This paper presents new experimental data obtained from the test facility installed at the Hera S.p.A. WTE plant in Forlì, Italy; discusses changes that can be implemented to increase the duration of experimental testing; offers suggestions for the design of an industrial solution.     

Comprehensive modeling of HFC-23 incineration in a CDM incinerator

Considering that a significant part of used refrigerants have to be destroyed in an environmentally friendly manner together with the high global warming potential (GWP) of HFCs (hydrofluorocarbons), the development of a proper incineration method of HFCs becomes one of the viable methods in the refrigeration and air-conditioning industry. To this end, in this study, the development of a comprehensive modeling of CHF₃ (HFC-23 or R-23) incineration is made to assist in the proper design and determination of optimal operating condition of a practical HFCs incinerator, since the refrigerant of CHF₃ is one of typical HFCs. For this, numerical investigation was performed by the development of a predictive model for the thermal destruction of the CHF₃ using CH₄–air flames in an incinerator designed for CDM (clean development mechanism) project. First of all, comparison between calculation and operation data was made to evaluate the program developed in this study. Numerical calculation of CHF₃–CH₄–air flame predicts successfully the operation data of a CDM incinerator such as temperature, CHF₃ destruction rate more than 99.99 % and other species concentrations such as CO and NO at the exit of the incinerator. Further parametric study was performed also in terms of important variables such as excess air, amount of steam and incinerator size. In general, the results obtained appear physically acceptable and give a clear physical insight into the role of the important variables. Further work is strongly recommended for the development of a general turbulent reaction model for the thermal destruction of HFCs, especially for the condition of non-equilibrium turbulent reaction dominance.     

On-line detection of metal pollutant spikes in MSW incinerator flue gases prior to clean-up

SUWIC's unique mobile metals emissions monitoring laboratory has been used to measure metal pollutant spikes in the flue gas from a municipal solid waste incinerator, prior to gas clean-up. The laboratory has a heated sampling probe that extends into the plant, allowing the simultaneous on-line measurement of the concentrations of more than 30 metals by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). As little is known about temporal variation in metal concentrations, this capability is seen as a major advance. The graphs of continuous measurements show that the elemental loading is far from uniform, and that concentrations fluctuate far more than may have been conventionally expected. There are occasional significant spikes in the emission profiles for cadmium and mercury, which are believed to be due to specific items in the waste feed material. Continuous monitoring measurements are of significant value for those seeking to model metal behaviour in combustion and in pollution control devices.     

The environmental fate of heavy metals arising from a MSW incineration plant

Pollutant fluxes from municipal solid waste (MSW) incinerators are of a certain concern, especially gaseous emissions from the stack, which constitute the major effluent from the plant. In this work, heavy metals in soil and vegetation sampled in different sites around the plant are compared with those found in the gaseous emissions from an incinerator: the suspected source and environmental matrices are observed together, in order to detect a possible relationship of cause and effect, using statistical methods. The incinerator examined, regarding dimension and technology, can be considered a typical Italian one. Heavy metal concentrations in soil and vegetation show a clear dependence on sampling year; similar behaviour can be found in emission fluxes referring to the same years. A dependence on the distance from the incinerator is also apparent. This study supplies a methodological approach that can be easily extended and applied to other suspected contamination sources.     

Calcium phosphate stabilization of fly ash with chloride extraction

Municipal solid waste incinerator by products include fly ash and air pollution control residues. In order to transform these incinerator wastes into reusable mineral species, soluble alkali chlorides must be separated and toxic trace elements must be stabilized in insoluble form. We show that alkali chlorides can be extracted efficiently in an aqueous extraction step combining a calcium phosphate gel precipitation. In such a process, sodium and potassium chlorides are obtained free from calcium salts, and the trace metal ions are immobilized in the calcium phosphate matrix. Moderate calcination of the chemically treated fly ash leads to the formation of cristalline hydroxylapatite. Fly ash spiked with copper ions and treated by this process shows improved stability of metal ions. Leaching tests with water or EDTA reveal a significant drop in metal ion dissolution. Hydroxylapatite may trap toxic metals and also prevent their evaporation during thermal treatments. Incinerator fly ash together with air pollution control residues, treated by the combined chloride extraction and hydroxylapatite formation process may be considered safe to use as a mineral filler in value added products such as road base or cement blocks.     

The use of commercial and industrial waste in energy recovery systems - A UK preliminary study

With 2020 energy targets set out by the EU fast approaching, the UK is trying to source a higher proportion of its energy from renewable resources. Coupled with this, a growing population and increasing trends in consumer demand have resulted in national waste loads increasing. A possible solution to both issues is energy-from-waste (EfW) technologies. Many studies have focused on municipal solid waste (MSW) as a potential feedstock, but appear to overlook the potential benefits of commercial and industrial waste (C&IW). In this study, samples of C&IW were collected from three North West waste management companies and Lancaster University campus. The samples were tested for their gross and net calorific value, moisture content, ash content, volatile matter, and also elemental composition to determine their suitability in EfW systems. Intra-sample analysis showed there to be little variation between samples with the exception two samples, from waste management site 3, which showed extensive variation with regards to net calorific value, ash content, and elemental analysis. Comparisons with known fuel types revealed similarities between the sampled C&IW, MSW, and refuse derived fuel (RDF) thereby justifying its potential for use in EfW systems. Mean net calorific value (NCV) was calculated as 9.47 MJ/kg and concentrations of sulphur, nitrogen, and chlorine were found to be below 2%. Potential electrical output was calculated using the NCV of the sampled C&IW coupled with four differing energy generation technologies. Using a conventional incinerator with steam cycle, total electrical output was calculated as 24.9 GWh, based on a plant operating at 100,000 tpa. This value rose to 27.0 GWh when using an integrated gasification combined cycle. A final aspect of this study was to deduce the potential total national electrical output if all suitable C&IW were to be used in EfW systems. Using incineration coupled with a steam turbine, this was determined to be 6 TWh, 1.9% of the national demand thereby contributing 6.5% towards the UK’s 2020 renewable electricity target.     

Variation in deformation properties of processed MSWI bottom ash: results from triaxial tests

This study is part of a larger study of the mechanical properties of processed municipal solid waste incinerator bottom ash. The aim was to investigate the variation in deformation properties of the ash for future use in unbound road layers. The effect of the material variation was analysed in particular. Specimens of bottom ash from four different incinerator plants and four sampling periods over a period of one year were tested by means of cyclic load triaxial tests. The results showed that there were variations in the deformation properties of the materials. Although there were significant differences between incinerator plants, the seasonal fluctuations were not significant. The differences were mainly due to the organic matter content. For the cyclic stress levels used, the resilient modulus ranged between 60 and 140 MPa, which is comparable to that of sand, but the plastic/permanent deformation was lower than for sand. It was also shown that the organic content has a limiting effect on the resilient modulus. For the material studied, the resilient modulus increased by 50% when the content of organic matter was halved.     

Does Soil Acidification Affect Spruce Needle Chemical Composition and Tree Growth?

In 1994, a large survey of soil chemistry was undertaken in thecounty of Värmland in central Sweden (Lundström et al., 1998).The southern part of the county was affected by soilacidification whereas there were no such indications in thenorthern part. To investigate the influence of soil chemistryon the trees at the specific sites, the survey was continued byan analysis of needle chemistry (Norway spruce) which wasundertaken at 150 of the 180 sites, and of tree growth at 65 ofthe 180 sites. Growth was expressed as a ratio between expectedgrowth, estimated with a national, empirical growth model, andthe growth observed in the field. In statistical analyses,using rank correlation, PCA and PLS, there were only weakindications of an influence of soil chemistry on needlechemistry and on tree growth. A moderate correlation betweennitrogen and sulphur in needles was found, which wasinterpreted as an effect of deposition and of processes in thetree canopy. No obvious regional pattern of the growth ratiowas found, in contrast to the clear pattern of soilacidification. The statistical analysis could not with anycertainty point out any of the soil chemistry variables asespecially important for the tree growth ratio.     

Modelling piloted ignition of wood and plastics

To gain insight in the startup of an incinerator, this article deals with piloted ignition. A newly developed model is described to predict the piloted ignition times of wood, PMMA and PVC. The model is based on the lower flammability limit and the adiabatic flame temperature at this limit. The incoming radiative heat flux, sample thickness and moisture content are some of the used variables. Not only the ignition time can be calculated with the model, but also the mass flux and surface temperature at ignition. The ignition times for softwoods and PMMA are mainly under-predicted. For hardwoods and PVC the predicted ignition times agree well with experimental results. Due to a significant scatter in the experimental data the mass flux and surface temperature calculated with the model are hard to validate. The model is applied on the startup of a municipal waste incineration plant. For this process a maximum allowable primary air flow is derived. When the primary air flow is above this maximum air flow, no ignition can be obtained.     

新型汽封在超临界600MW机组的应用

介绍了一种新型汽封在国产600 MW机组节能改造中的应用。改造方案为将汽轮机组原通流部分及轴端的梳齿型汽封改为新型接触式密封齿＋蜂窝汽封＋铁素体齿的组合汽封,改造后漏汽量大幅减少,高、中、低压缸效率和机组运行的经济性明显提高,对同类型汽轮机通流部分节能改造具有较好的借鉴意义。     

Integrated drying and incineration of wet sewage sludge in combined bubbling and circulating fluidized bed units

An original integrated drying and incineration technique is proposed to dispose of sewage sludge with moisture content of about 80% in a circulating fluidized bed. This system combines a bubbling fluidized bed dryer with a circulating fluidized bed incinerator. After drying, sewage sludge with moisture less than 20% is transported directly and continuously from the fluidized bed dryer into a circulating fluidized bed incinerator. Pilot plant results showed that integrated drying and incineration is feasible in a unique single system. A 100 t/d Sewage Sludge Incineration Demonstration Project was constructed at the Qige sewage treatment plant in Hangzhou City in China. The operational performance showed that the main operation results conformed to the design values, from which it can be concluded that the scale-up of this technique is deemed both feasible and successful.     

Stochastic modeling and optimization of medical waste collection in Northern Jordan

Jordan has witnessed a rapid increase in healthcare facilities during the last two decades. As a consequence, the amount of generated medical waste have been increased rapidly and a proper management system is indeed needed to eliminate the environmental and health hazards resulted from such waste. An approved medical waste treatment facility is the incinerator located at the northern region of Jordan which serves the four northern governorates. Two trucks are used to pickup waste from the hospitals in these governorates to be treated at the incinerator. In this paper, a route scheduling model is proposed to minimize the total travel distance which in turn minimizes transportation cost and reduces emissions. The proposed model takes into account the capacity of trucks, number of visits per week, timing between visits along with the service level required by the hospitals. An optimal routing schedule was found and verified. Compared to current routing schedule, a saving of 102 km per week was achieved.     

An LCA model for waste incineration enhanced with new technologies for metal recovery and application to the case of Switzerland

A process model of municipal solid waste incinerators (MSWIs) and new technologies for metal recovery from combustion residues was developed. The environmental impact is modeled as a function of waste composition as well as waste treatment and material recovery technologies. The model includes combustion with a grate incinerator, several flue gas treatment technologies, electricity and steam production from waste heat recovery, metal recovery from slag and fly ash, and landfilling of residues and can be tailored to specific plants and sites (software tools can be downloaded free of charge). Application of the model to Switzerland shows that the treatment of one tonne of municipal solid waste results on average in 425 kg CO₂-eq. generated in the incineration process, and 54 kg CO₂-eq. accrue in upstream processes such as waste transport and the production of operating materials. Downstream processes, i.e. residue disposal, generates 5 kg CO₂-eq. Savings from energy recovery are in the range of 67 to 752 kg CO₂-eq. depending on the assumptions regarding the substituted energy production, while the recovery of metals from slag and fly ash currently results in a net saving of approximately 35 kg CO₂-eq. A similar impact pattern is observed when assessing the MSWI model for aggregated environmental impacts (ReCiPe) and for non-renewable resource consumption (cumulative exergy demand), except that direct emissions have less and no relevance, respectively, on the total score. The study illustrates that MSWI plants can be an important element of industrial ecology as they provide waste disposal services and can help to close material and energetic cycles.     

Evaluation of in situ steam‐injection processes for reduction of petroleum compounds within an abandoned canal

A conceptual approach of a novel application of in‐situ thermal processes that would either use a steam injection process or a steam/surfactant injection process was considered to remediate petroleum contaminated sediment residing in an abandoned canal. Laboratory tests were conducted in an attempt to volatilize or mobilize contaminants of concern (selected polycyclic aromatic hydrocarbons [PAHs]) from the contaminated sediment into a phase that could be physically removed. The processes were operated above ambient temperature and pressure in an attempt to increase the removal of the contaminants of concern from the sediment. The ability of both the steam injection process and the steam/surfactant process to remove PAHs from the sediment was considered ineffective; as only two of the seventeen selected PAHs (naphthalene and C1 naphthalene) were associated with a percentage mass reduction greater than 34% for both treatments (four trials). The steam/surfactant injection process generally resulted in higher reductions than the steam injection process, but had larger variances within the two trials using the treatment type. This preliminary evaluation suggests that steam‐based injection processes for removing petroleum contamination from this canal sediment, using the surfactants selected, equipment set‐up, and operating conditions studied, would be considered ineffective. © 2010 Wiley Periodicals, Inc. *

1 This article is a U.S. Government work and, as such, is in the public domain of the United States of America.

     

Characterization of municipal solid waste combustion in a grate furnace

The objective of this paper is to evaluate the combustion process of municipal solid waste combustion in a grate furnace both experimentally and numerically by using data of a reference experiment with over-stoichiometric primary air supply. Measurements were carried out inside the combustion chamber of a pilot plant by monitoring temperatures and sampling gaseous combustion products along the bed surface. The data were assessed using elemental and energy balances. Experimental data of the axial temperature profiles of the flue gas, the fuel bed and the grate bars, as well as local gas flows and the flue gas composition measured above the fuel bed along the grate were used to describe the conversion process, including drying and carbon burnout. These data served as input to model the thermo- and fluid dynamic processes of the gas phase above the bed inside the combustion chamber. For this purpose the commercial code FLUENT was employed to carry out the simulations. Thus, the turbulent temperature, flow and species distributions in the combustion chamber of the pilot waste incinerator TAMARA were predicted. The results of the FLUENT modeling showed that under the prevailing conditions the flue gas burnout is almost completed before entering the first flue due to high temperatures, effective mixing and sufficient residence times of the flue gas inside the combustion chamber. This agrees well with the experimental results inside the first flue. On the basis of the above mentioned results, design and parametric studies can be carried out in a more efficient way by saving cost and time.     

An investigation on the potential of metal recovery from the municipal waste incinerator in Taiwan

This study aimed to identify distribution of metals and to estimate the amount of these metals that can be potentially recovered from incineration residues. First, the partitioning behavior of Cr, Cu, Fe, Cd, Al, Zn, and Pb in bottom ash and fly ash was investigated in one large municipal waste incinerator in Taiwan. In addition, the material flow analysis (MFA) method was used to estimate the material flux of metals within incinerator plant, and to calculate the amount of metal recovery. According to the findings of this study, six metals (Fe, Al, Cu, Zn, Cr, and Pb) concentrated in bottom ash mostly, while Cd existed primarily in fly ash. The weight percentages of Fe (4.49%), Al (5.24%), Cu (1.29%), Zn (2.21%), and Pb (0.58%) in incinerator ash are high, and even higher than the compositions of natural minerals. Finally, the amount of Cr, Cu, Fe, Cd, Al, Zn and Pb that can be potentially recovered from incineration residues will reach 2.69 x 10(2), 1.46 x 10(4), 4.91 x 10(4), 6.92 x 10(1), 5.10 x 10(4), 1.85 x 10(4) and 4.66 x 10(3) ton/yr, respectively.     

SLP250二段式垃圾焚烧炉的燃烧调整

由于垃圾的热值和干、湿度等变化较大,所以,垃圾焚烧炉的燃烧调整具有一定的难度。简要论述了如何调整和控制垃圾焚烧炉的稳定燃烧,以供相关人员参考。     

A comprehensive approach to plume stability

This article defines and presents a systematic approach to groundwater plume‐stability assessment. Qualitative and quantitative methods that have been used to assess plume stability at National Priority List sites undergoing optimization are reviewed. Example case studies are included to illustrate the advantages of combining multiple analysis methods. Relevant statistical methods include identifying normal data distributions, detection frequencies, coefficients of variation, individual well trends, and rates of change at individual monitoring locations. Trend estimates for total plume mass and center of mass provide a broader picture of plumewide processes. Deterministic methods, such as quantitative mass‐balance approaches, may be useful for larger plumes. Qualitative assessments include evaluations of the conceptual site model, source strength, attenuation mechanisms, and hydrogeology. Because groundwater plumes are always dynamic, the determination of plume stability has to include qualitative steps relating the rate and magnitude of change to the goals and objectives of the program and the time frame over which critical management decisions are to be made. The assessment of plume stability is, therefore, presented as a process that should involve both qualitative and quantitative steps for determining the acceptability of variability in groundwater contaminant concentrations. © 2010 Wiley Periodicals, Inc.     

Alternative strategies for energy recovery from municipal solid waste Part A: Mass and energy balances

This two-part paper assesses four strategies for energy recovery from municipal solid waste (MSW) by dedicated waste-to-energy (WTE) plants generating electricity through a steam cycle. The feedstock is the residue after materials recovery (MR), assumed to be 35% by weight of the collected MSW. In strategy 1, the MR residue is fed directly to a grate combustor. In strategy 2, the MR residue is first subjected to light mechanical treatment. In strategies 3 and 4, the MR residue is converted into RDF, which is combusted in a fluidized bed combustor. To examine the relevance of scale, we considered a small waste management system (WMS) serving 200,000 people and a large WMS serving 1,200,000 people. A variation of strategy 1 shows the potential of cogeneration with district heating. The assessment is carried out by a Life Cycle Analysis where the electricity generated by the WTE plant displaces electricity generated by fossil fuel-fired steam plants. Part A focuses on mass and energy balances, while Part B focuses on emissions and costs. Results show that treating the MR residue ahead of the WTE plant reduces energy recovery. The largest energy savings are achieved by combusting the MR residue "as is" in large scale plants; with cogeneration, primary energy savings can reach 2.5% of total societal energy use.